flat top thickness

[em guitars]

Hi all, I'm a new guy here, and new to the world of mandolin. I've been building guitars, basses and other unusual instruments for about 16 years now, even built a couple of mandocellos, they can be seen on Mr Mando's site emando.com. (look up Eric Mundt in the builder's section)
Anyway, as previously stated, I'm new to mando, and I'm currently working on a flat top. I'm curious as to what an appropriate final thickness should be for the top and back. I'm guessing somewhere in the .125" range, but I'm pretty much clueless. Any tips, hints, tricks, anything in particular I want to be looking out for would be greatly appreciated.
This is an awesome website, by the way! Everyone seems so friendly and helpful, and the amazing instruments I've seen are a constant inspiration! I'm glad I found this place!
Eric.

[sunburst]

Depends on how stiff the wood is, how big the mandolin is, how the top is to be braced, whether induced arch or canted top, fixed or floating bridge, and so forth. Generally, similar to a guitar top or perhaps a little thinner.

[em guitars]

Thanks John, knowing that I'm looking to guitar top thickness as a reference point gives me a good starting place. Luthier's Mercantile offers a service where they will thickness sand tops purchased from them to a thickness of .110 - .120, depending on the type of wood, so I'm gonna start there.
Another question, if I may. I've seen that, unlike guitar tops, where the bracing extends under the kerfing, mando bracing stops short of that. Is that to keep the top from being too stiff? I want to use tone bar type bracing on this instrument, so how far from the edge should my braces stop? And if what I've read so far is accurate( and I have no reason to believe it isn't) they should be mounted under the area where the feet of the bridge sits, yes? Thanks again, I'll post some pictures as it progresses.
Eric.

[sunburst]

You've left me behind here, I don't know of F-hole archtop type tone bars (lengthwise the top) being commonly used in flat tops. The tone bars used in arched mandolins are sort of adapted from the violin bass bar which does indeed stop well short of the lining, but I've seen mandolin tone bars done both ways; stopped short, and with the ends tucked under the lining or kerfing sort of like guitar braces. Lots of people X-brace flat tops and they usually place the arms of the X so that the bridge sits above them, the old Army Navy flat tops had a single transverse brace with nothing under the top at the bridge location, if I remember correctly.
Basically, you're on you own designing your bracing pattern.

[thistle3585]

I went .090 on my last flat top and I used two transverse braces, one of which was about an inch in front of the bridge. I just switched to .080 on my ukes. I believe Graham McDonald discussed this once before and described how the bridge is pulled forward and down, so if the brace is at or behind the bridge then the top will sag. I've seen this happen on several flat tops, and an induced arch didn't seem to help much either. I know some instruments have a soundhole patch to help strengthen the top in that area. I think Graham McDonald has the most definitive books on building flat tops.

[em guitars]

Thanks guys, I probably should have mentioned that I'm not using a central soundhole, but rather two holes in the F hole locations. They're not exactly F shaped, though. This is the first instrument in a long while that I'm building for myself, and as such I thought I'd experiment. I have no idea if it will come out as I planned, but the process certainly is fun!
Eric.

[sebastiaan56]

Page 60 of "The Mandolin Project" by Graham McDonald states "A spruce soundboard need to be brought down to about 3mm, 1/8 inch and 3.5-4mm for Western Red cedar. Note that Graham recommends a 15' radius for the soundboard.